1. Field of the Invention
This invention relates to a focus detecting camera with a display and more particularly to a device which is capable of displaying the direction of the drive of the camera's photo-taking lens.
2. Description of the Prior Art
Known photographic cameras with focus detecting circuits use the computation performed by a focus detecting circuit to determine whether the drawn out or drawn in position of a photo-taking lens is in a near-focus, an in-focus or a far-focus position. Cameras with such conventional focus detecting circuits utilize one of two methods, i.e., a fully automatic method in which the photo-taking lens is automatically driven to shift it toward an in-focus position on the basis of the result of the computation performed by the focus detecting circuit; or a manual method in which the photographer moves the photo-taking lens either manually or by power according to a display indicating a near-focus, in-focus or far-focus state.
Although it varies with the distance measuring method employed for the focus detecting circuit, cameras with conventional focus detecting circuits generally have a limited focus detecting range and are incapable of detecting a focus under various conditions such as when an object to be photographed is dim, when the actual lens position deviates significantly from its in-focus position, when the objects contrast is weak, when the object is composed of a fine repeating pattern, and so on. In such conditions, the operation of the camera varies greatly depending upon the extent of the departure of the actual lens position from the in-focus lens position. At certain drawn out positions of the photo-taking lens, an operation which draws the lens in or out makes it possible for the focus detecting circuit to detect the focus condition as the lens moves closer to the in-focus position even if focus detection is impossible at the initial lens position. Therefore, when automatic focus detection is ordinarily impossible, forcibly driving the photo-taking lens in an arbitrary direction initiates a so-called searching operation which makes focus detection possible.
When a conventional camera with a focus detecting function is in the search mode either nothing is displayed within the viewfinder or a display merely shows that the camera is in the process of searching. Hence, the photographer is unaware of the direction in which the searching operation is drawing the lens in or out. Therefore, even when the photo-taking lens is being shifted away from the focusing direction during the searching process, the photographer is unable to know it. This tends to delay his or her decision to switch the camera to a manual focusing operation mode or to reverse the search direction in order to seize a momentary picture-taking opportunity.
When focusing manually, the photographer drives the photo-taking lens on the basis of a near-focus or far-focus display. In that case, the absence of a display indicating the drive direction of the photo-taking lens compels the photographer to perceive the actual lens drive direction only from the near-focus or far-focus position through the gradual focusing or defocusing of the lens. Therefore, manual focusing has required a long time especially when the lens is being driven away from the focused condition. This has also presented a problem.